Merge branch 'ps/refspec-wo-the-repository'

Merge branch 'ps/refspec-wo-the-repository'

The dependency on the global 'the_repository' variable in the
'refspec.c' API has been removed by passing the hash algorithm
explicitly to refspec-parsing functions and storing it in 'struct
refspec'.

* ps/refspec-wo-the-repository:
  refspec: stop depending on `the_repository`
  refspec: let callers pass in hash algorithm when parsing items
  refspec: group related structures and functions